[NLRS] Club Cheap Yagi Build Day Advice Needed

Wed Nov 16 23:49:21 EST 2016

Thanks all for your comments!  I appreciate the feedback, and will be
moving forward with the build project soon.  I am aiming to have it
accomplished in time to get the club members on the air for the
January VHF contest.

Regards,
  Bill
AE0EE, EN34

On Wed, Nov 16, 2016 at 10:25 AM, Dr. Gerald N. Johnson
<geraldj at netins.net> wrote:
>
>
> The wire diameter does affect the length of the elements so should match
> Kent's original.
>
> Brazing rod from a welding shop I have used but it was often irregular in
> cross section, rarely round so its harder to fit in a drilled hole.
>
> For more permanent antennas I like K1FO designs like were in ARRL handbooks
> for a long time. They do work well. K1FO didn't approve of shorter ones not
> having optimized them but I've found through modeling that tne 9 element
> gives more gain than a Msquared 12 element and does it with a shorter boom,
> like 10 feet at 2m or 1m boom at 432 and the 432 version measured more gain
> at CSVHF than the model showed.
>
> Its important to correct element lengths for metal booms and for element
> diameter using the data from Pfisbecke's NBS report or G3SEK (now GM3SEK)
> program element.bas. I have it here as a windose command window element.exe
> from compiling the basic program, I believe.
>
> 73, Jerry, K0CQ
>
>
> On 11/15/2016 11:14 PM, James Duffey wrote:
>>
>> Jerry - I never used #10, but I know that #8 and #6 copper wire works fine
>> on the WA5VJB antennas with little or no sag. I used that size wire with no
>> special treatment on my WA5VJB antennas that I used roving and they held up
>> to Interstate Highway speeds or a bit more with few problems. Hitting low
>> hanging trees and canopies did bend them, but they could be easily be bent
>> back. To be honest, taking the antennas off and on the rover resulted in the
>> elements looking a bit bedraggled, but that did not affect their electrical
>> performance.
>>
>> The original antennas by WA5VJB and the first ones I made were from #8
>> aluminum TV ground wire then available from Radio Shack in a 50ft roll
>> pretty cheap. $8? Those elements were far less sturdy than the copper wire
>> ones I built and really looked ragged. But they worked.
>>
>> The three element VJB 2M antennas all require lengths greater than 3ft,
>> which require splicing on an extension, which is where the exercise begins
>> to deviate a bit from easy and may be a hassle if you are trying to help 8
>> or 10 people of varying mechanical and electrical skills make an antenna in
>> an evening.
>>
>> Having said that, I have made the antennas from 1/8in dia, 3ft long,
>> bronze brazing (weld?) rod with small extensions on the end and they work
>> well. I crimped the tubing on and then soldered it. The 3ft weld rod is
>> suitable on higher frequencies, 220MHz and up, without the extensions and is
>> probably the cheapest source of elements available. I bought the rod at Ace
>> Hardware.
>>
>> After Radio Shack discontinued the aluminum grounding wire I used 1/8 inch
>> aluminum weld rod, again from Ace Hardware. Those antennas went together
>> well and worked fine. The elements stayed straight even after hitting trees
>> and canopies. They looked nice. But all those miles at speed took their
>> toll. The aluminum work hardened and became brittle and even the slightest
>> touch would break the elements. I switched those elements to the bronze weld
>> rod as they broke. I suppose that this is not too surprising as the weld rod
>> is not made from a structural alloy.
>>
>> I have moved on from the VJB antennas for my rover as W7QQ designed and
>> built some 8ft rover antennas. Still I have a few in the spare antenna pile
>> and I always recommend them to beginners, particularly if they don’t want to
>> invest a lot of money to see if they are interested in weak signal VHF/UHF
>> operation.
>>
>> I never thought of the VJB antennas in terms of longevity. By the time
>> they start to deteriorate most operators will want to move up to longer boom
>> antennas, either longer VJB antennas or aluminum antennas with a longer
>> boom. - Duffey KK6MC
>>
>>
>> On Nov 15, 2016, at 9:29 PM, Dr. Gerald N. Johnson<geraldj at netins.net>
>> wrote:
>>
>>>
>>>
>>> 3/16" brass rod 3 feet long can be found at some farm stores, good
>>> hardware stores, and hobby shops. Maybe even big box home stores, at
>>> Menard's in the hardware department next to steel and aluminum bars and
>>> rods, not the eletrrical department. The middle two places can carry K&S
>>> Engineering products. And the hobby shop brass (also available on line
>>> without the K&S numbers but the same sizes at McMaster-Carr,
>>> www.mcmaster.com) has tubing in 12" and 36" lengths with 1/64th wall in
>>> telescoping sizes. So 3/16" tubing is easily spliced with a bit of 5/32"
>>> tubing inside at the soldered splice. The tubing won't bend in the U shape
>>> though. I'm sure Kent lists the wire sizes and the wood sizes he has used.
>>>
>>> 3/16" ID brass tubing, 7/32" OD can extend 3/16" tubing or solid rod on
>>> the outer ends of the slements.
>>>
>>> #10 copper wire will probably sag on horizontal elements not being
>>> hardened like brass tubing. Of course the director and reflector can be
>>> aluminum rod or tubing probably readily available at the sources mentioned
>>> by Donn. Copper wire can be work hardened by stretching it.
>>>
>>> Varnish is important to longevity of wooden boom antennas. Bare brass and
>>> copper elements survive longer if painted with something like clear Krylon
>>> or Rustoleum or clear epoxy paint if it can be found.
>>>
>>> 73, Jerry, K0CQ
>>>
>>> On 11/15/2016 7:14 PM, W. S. Mitchell wrote:
>>>>
>>>>
>>>>
>>>> Greetings,
>>>>    I am organizing a WA5VJB Cheap Yagi build day for the Bloomington
>>>> (MN) Amateur Radio Association, which will happen at some point in the
>>>> next few months.  However, having never built these antennas before, I
>>>> could use some advice.
>>>>
>>>> Assume for a moment that there are 8 participants, each of whom is
>>>> interested in building a 3-element 2 m yagi.  Each antenna requires
>>>> roughly 12' of conductor, with lengths of 37" (director), 41"
>>>> (reflector), and 60" (driven).
>>>>
>>>> Am I correct to think that the best way to approach this is to use #10
>>>> solid copper wire for the whole thing?  I've looked for welding rod,
>>>> and it seems like it's more suited for 222 MHz and above (hard to find
>>>>>
>>>>> 36" pieces).  From my searching, 1/8" or 3/16" copper tubing are a
>>>>
>>>> bit tricky to find as well, and is generally more expensive (and less
>>>> robust in the field) than the (admittedly thinner) solid stuff.
>>>>
>>>> My hardware store has 1/2"x3/4" pine in 8' sections, which should be
>>>> good for a few antennas.  I already have coax that can be used, and
>>>> tracking down crimp-type connectors (BNC, PL-259, probably not N
>>>> because the club members are unlikely to have any N gear) shouldn't be
>>>> too difficult.
>>>>
>>>> Any advice or suggestions on sourcing materials would be greatly
>>>> appreciated.
>>>>
>>>> Thanks,
>>>>    Bill
>>>> AE0EE
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>>>
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>>
>>
>>
>>
>
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